During the manufacture of complex structures, such as aircraft, dimension checks are commonly performed on a structure to ensure that it conforms to plan, taking into account manufacturing tolerances. Such dimension checks may be performed using callipers, rules or other devices to take the required measurement from the structure to compare to the corresponding plan. One problem is that such checks may need to be performed in difficult to reach or constricted spaces thus making accurate measurement difficult. For example full sight of the structural elements being measured may not be possible making accurate positioning of a calliper or rule difficult and error prone.